The High Voltage Electron Microscope Facility is a Biotechnology Resource of the Biotechnology Resources Branch of N.I.H. and is available to bio-medical researchers for ultrastructural studies where use of a high voltage electron microscope can provide new information. Investigations are directed especially towards analysis of relatively large and complex three-dimensional cell structures either in intact cells or isolated organelles, such as isolated flagella, chromosomes and Golgi complexes, or in sections up to 1 or 2 microns thick. The cold stage will undergo further development and modification. Freezing and cold sample handling procedures have been developed for viewing frozen sections, whole specimens, isolated cell components and aqueous suspensions. An improved type of image intensifier and digital image/memory processor has been installed and successfully used. This is part of a program to improve resolution and performance at high magnification in order to make possible high resolution studies of macromolecular crystals. The H.V.E.M. is particularly well suited to high resolution studies of this type because of its greater penetrating power, its greater depth of field and because of its greater specimen chamber size, one sufficiently large to permit introduction of ancillary equipment such a tilting/cooling stages which are necessary to preserve and orient these biological structures. Methods are being developed for immunocytochemical labeling of cell structures such as cytoskeletal elements, both in cell whole mounts and in thick sections.